A display system presently in use under such circumstances for leak detectors comprises two parallel rectilinear strips, one of which is graduated in various negative powers of ten and the other is graduated from 0 to 10, giving the value of the multiple for the negative power of ten as displayed on the first strip.
Such a display system suffers from the drawback of requiring two display strips to be observed in succession, and in the event of the value of the signal varying rapidly over a range covering several powers of ten, the strip graduated from 0 to 10 rises very quickly and several times in succession, starting again from zero on each occasion, giving rise to a disagreeable flashing effect.
Another known display system has one window in which a rough value for the signal is displayed, specifying the power of ten range for the value of the signal, and a circular strip for giving the multiple in the range 1 to 10 for said power of ten.
In that case also, the observer needs to look at two distinct locations and the rapid rotation of the index mark on the circular strip in the event of large variation in the value of the signal is likewise quite misleading.